Image translating device



Oct. 28, 1947. J. w. GIBSON IMAGE TRANSLATING DEVICE Filed Aug. 8, 1945(re-1.5mm

REPRODUCER VIEWING S C RE is N ELECTROMAGNETIC LENS ATTONK Patented Oct.28, 1947- IMAGE TRANSLATING DEVICE James W. Gibson, Avenel, N. J.,assignor to Western Electric Company, Incorporated, New York, N. Y., acorporation of New York" Application August 8, 1945, Serial No. 609,668

6 Claims. (01. 178-7.2)

This invention relates to an image translating device and moreparticularly to means for translating an invisible image formed withshort radio waves into a visible image or into a plurality of electricpotential values from which a record or reproduction of an object orscene can be obtained.

Arrangements have been disclosed in the past whereby an invisible imagemay be formed by means of short radio Waves collected from an object orscene by a lens, using technique similar to that used with light rays ina camera. Means have been shown for causing an invisible image of thissort to produce induced currents in small circuit elements distributedover the field of the image and arrangements have been shown wherebysuch induced currents might be used directly to produce flashes of lightwhich combine to form a visible image corresponding to the object orscene from which the invisible image was formed. Apparatus has also beendisclosed for translating an invisible image formed with infra red. orultra violet light rays into a visible image. In the field of televisionon the other hand, light-sensitive screens or mosaics have beendeveloped for translating a visual image into a plurality of electricpotential values or electric charges which in turn may be translatedinto picture impulses or video currents upon causing the mosaic to bescanned by a cathode ray. The .video currents may be employed toreproduce the visual image in the same or another location according towell-known television technique by transmitting the video currents andusing them to control the reproducing system.

An object of the present invention is to adapt the television technique,as employed with visible light rays so that the technique may 'be usedin a system of television wherein short radio waves take the place oflight rays between the object to be viewed and. the image of that objectwhich it is desired to reproduce.

A feature of the invention is an improved means for translating aprimary, invisible image formed with short radio waves into a secondary,visible image.

Another feature is a rectifying element suitable for rectifying surfacecurrents or eddy currents.

The invention is particularly applicable to a system for viewing adistant scene through darkness or fog, etc., by means of an image formedwith electromagnetic waves, the image being translated into a pluralityof electric charges by means of a mosaic of rectifying elements, saidelements being discharged successively as by a scanning beam ofelectrons to form a video current which may be employed in known mannerto form a secondary image which latter may be visual.

The invention is particularly adapted, but not limited, to use withelectromagnetic waves of the order of 1 centimeter wavelength.

The scope of the invention is defined in the appended claims and theinvention is more fully described hereinafter in connection with theaccompanying drawing in which:

Fig. 1 shows an embodiment of the invention in a viewing system; and

Fig. 2 shows an enlarged perspective view of a rectifying elementaccording to the invention, combined with a diagram useful in explainingthe operation of the invention.

Referring to Fig. 1, 10 represents an electromagnetic lens arranged togather radiation of short radio waves from an object represented by anarrow I I and to form an invisible image represented by another arrowl2.

A conductive plate l3 having attached thereto a plurality of rectifyingelements 14 forming a planar array or mosaic is placed in such aposition that the image I2 is cast upon the elements I' l. The plate I3and elements M are enclosed in an evacuated envelope l5 having a neckportion l6 containing the usual elements of a cathode ray scanningdevice in operative position to scan the mosaic of elements 14. Therectifying elements I4 are each conductively attached to the plate [3which in turn is conductively connected to ground through a lead I! andan impedance element represented by a resistor [8. A cathode lead [9 forthe scanning system is grounded as at 20. The resistor I8 is connectedto a video amplifier 2!, or the resistor may constitute an elementincluded in the amplifier 2|, which latter is in turn to be connected toa television reproducer 40 which may be of conventional design, having aviewing screen 4|. To save space in the drawing, the televisionreproducer and viewing screen are shown schematically only and not toscale, these elements being of conventional deslgn.

One of the rectifying elements 14 is illustrated on an enlarged scale inFig. 2. The element [4 is preferably spherical and may be a copper ball.A portion 30 of the surface of the element l4, preferably a hemisphere,may be the untreated copper. The remainder of the surface, indicated at3|, has an exposed surface of cuprous oxide as in the conventionalcopper-oxide rectifier.

The elements M are all to be oriented with the ties at their junction.

In the operation of the system disclosed in thedrawing, electromagneticwaves are reflected from the object or scene represented by the arrowII, which object or scene may be irradiated by any suitable source ofshort radio waves either at the receiving station or elsewhere such as adipole antenna 50 located at the focus of a parabolic reflector theradiation from which may be directed toward the object or scene. Also,the object may, of course, be a generator and radiator of such waves.The waves from H are collected by the lens I0 and formed into aninvisible image or pattern of electromagnetic waves at I! in the planeof the rectifying elements M. The square 32 in Fig. 2 represents aportion of a plane of a radio frequency wave front traveling in thedirection of the arrow 33, the electric vector of the field beingindicated by the arrow 34 and the magnetic vector by the arrow 35. Asthe plane 32 of the wave passes the rectifying element l4, electron flowis set up on the surface of the element [4 in the direction as indicatedby arrows 3B in Fig. 2. The lines of electron flow may be generallydescribed as circular. Since there is low resistance to electron flowfrom the copper to the oxide across the rectifying boundary and highresistance in the opposite direction, the result is an accumulation ofelectrons, that is, a negative charge" on the back surface of the sphereat 3| and, hence a. deficiency of electrons, that is, a positive chargeon the front at the surface 30. The mosaic of elements l4, having theradio frequency image or pictures focussed upon it, by virtue of theaccumulated charges transforms the image into an electrical picture, thefront half of each element assuming a positive potential proportional tothe radio frequency intensity at that point. The mosaic may hey-scannedby a cathode ray from the neck portion iii of the vacuum container. Whenso scanned, each element I4 is discharged in turn, the resultingelectron flow passing into plate i3 thence through the resistor l8 toground and cathode lead I9. The potential drop across. the resistor 18due to the discharge current is impressed upon the input of the videoamplifier 2|. A succession of pulses is thus supplied to the videoamplifier 2! during the scanning operation and these pulses convey thenecessary information to the television reproducer 40 to form upon theviewing screen M reproduction of the invisible image [2. Betweensuccessive contacts with the scanning beam, each element [4 is rechargedby the then existing field at the location of the element in question.The scanning should proceed at a uniform, steady rate to avoid flickerand distortion in the visual image.

The lens Ill may be of any conventional construction suitable for therefraction of radio waves of the wavelength employed. It is known thatthe refractive properties of an optical lens result 4 from the fact thatthe velocity of light in the 4 optical material such as glass is lessthan the velocity of light in air. By definition, i=V/V', where i is theindex of refraction of the medium, V is the velocity of light in air andV' is the velocity of light in the medium. Passing to electromagneticwaves in general, the velocity of the wave in a ny medium is given bythe expression V'=1 /k;t, where k is the dielectric constant of themedium and a is the permeability of the medium. By combining these twoequations and taking into account that the dielectric constant for airis unity and that the permeability for air and for all non-magneticmedia is also substantially unity, it follows that i=\/i?. Using thisrelationship to design a double convex lens to be formed, for example,from porcelain (dry process) results in a lens having a radius ofcurvature of 13 feet and a focal length of 3.74 feet. A lens of thisdesign is adapted to form an image 2' feet square from an object 5 milessquare at a distance of 50,000 feet, as for example from an airplane atthat altitude.

It is known from wave theory that two points of an image formed by anylens system in air, in order to appear separate and distinct, must beseparated by at least \/2, where A is the wavelength of the radiationforming the image. This represents the theoretical maximum resolutionwhich in practice can only be approached. A lens of the dimensions givenabove, when used with l-centimeter radiation may be expected to give adegree of definition comparable to that. in a 120 line televisionpicture.

The element I4 may have a diameter approaching one-half wavelength asanupper limit imposed by the theoretical maximum resolution, butpreferably the diameter of the element l4 should be considerably smallerand the individual elements [4 should be mounted as close together aspossible to insure maximum definition in the final visible picture.

Using l-centimeter radiation, the maximum diameter of the element I 4 asdetermined by the theoretical maximum resolution is one+half centimeter,or approximately one-fifth of an inch. As stated above, the elements [4should preferably be made considerably smaller in order that several ofthem may be set in the space of one-half centimeter.

In terms of an object which is 5 miles square,

' such as an area of terrain, the resolution in a system employinl-centimeter waves has a theoretical value of 200 feet.

It will be noted that, to promote legibility in- Fig. 1, the amount ofseparation between the elements It is exaggerated beyond what isnecessary to avoid danger of contact. Also, only a few elements 14 arepictured, whereas many such elements and rows of elements will berequired depending upon the dimensions of the image l2.

It will be understood that in the operation of in which the device ispointed will show the direction to the source or reflecting object.

It will be further evident that the element I 4 is useful apart from thesystem described, in any application calling for a rectifier forelectric currents such as eddy currents induced in the surface of anelement.

Modifications of the system disclosed, within the scope of the appendedclaims will occur to one skilled in the art and additional uses willappear which may be made without exceeding the limits of the claims.

What is claimed is:

1. A translating system comprising a conductive plate, a plurality ofspaced spherical elements each having a hemispherical surface portion ofcopper and having the remaining surface portion of cuprous oxide, eachof said spherical elements having the cuprous oxide surface portionthereof conductively attached to said plate, means projecting upon saidspherical elements a pattern of electromagnetic waves of wavelength ofthe order of magnitude of the diameter of one of said spherical elementsto accumulate electric charges on the respective hemispherical surfaceportions of said spherical elements, means neutralizing the charge onthe unoxidized copper surface portion of the spherical elements insuccession, and a return circuit from said conduc tive plate to saidneutralizing means for indicating variations in the accumulated chargesfrom one spherical element to the next.

2. A translating system comprising a conductive plate, a plurality ofspaced spherical elements each having a hemispherical surface portion ofcopper and having the remaining surface portion of cuprous oxide, eachof said sph/erical elements having the cuprous oxide surface portionthereof conductively attached to said plate, cathode ray scanning meansin position to scan said spherical elements successively, and a returncircuit from said conductive plate to the cathode of said scanningmeans, said return circuit including video current responsive means. 7

3. A system for transforming a primary image formed by electromagneticwaves into a secondary image formed by other electromagnetic waves, saidsystem comprising a plurality of spaced rectifying elements each havinga conductive surface divided into two portions separated by a rectifyingboundary region, means supporting said rectifying elements in the formof a mosaic lying substantially in the plane of the primary image, eachsaid rectifying element being arranged to have its direction of bestconduction substantially p rpendicular to the plane of the primary imageand said elements being poled with the conductive direction of eachelement the same as any other with respect to the said plane, wherebythe electric field variations atany given point in the primary imagegive rise to surface alternating currents on a particular one of saidrectifying elements thereby accumulating an electric charge on one sideof said rectifying boundary in proportion to the electric fieldintensity at the given point, means periodically discharging saidrectifying elements in succession thereby producing a fluctuatingcurrent varying in accordance with the magnitude of the accumulatedcharge from element to element, and means producing a secondary imagefrom the information carried by the fluctuations in said current.

4. A rectifier for surface currents induced by 7' electromagnetic waves,said rectifier comprising a spherical element the diameter of which isof the same order of magnitude as the wavelength of the waves and thesurface of which is divided into two hemispheres one of which is cuprousoxide and the other unoxidized copper.

5. A combined antenna and detector for electromagnetic waves, comprisinga spherical element of diameter of the order of magnitude of thewavelength of the wave to be detected, the

surface of which spherical element is composed REFERENCES CITED Thefollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,049,472 Rosett Aug. 4, 19362,140,994 Gorlich Dec. 20, 1938 2,149,977 Morton Mar. 7, 1939 2,065,570Essig Dec. 29, 1936 2,171,213 Janes Aug. 29, 1939 2,246,328 Smith June17, 1941 Liebel Apr. 25, 1933

